2008 Mercury Mountaineer power steering quits when A/C is on

2008 Mercury Mountaineer v6 AWD, ~145k miles. It's been working okay lately, considering. Now power steering pump pulley stops turning when I turn the wheel while the A/C is on. No steering boost while A/C compressor is engaged. Also has a moderate leak from the water pump.

Replaced tensioner, idler, and belt. Applied belt dressing to the new belt. Power steering pulley still comes to a stop with the A/C on when I turn the wheel. Now the alternator sometimes stops--battery light comes on--when the A/C is on. Any ideas?